Storage tanks for commercial and industrial purposes are widely used for storing a variety of liquids. These storage tanks may either be located above or below ground and are adapted to contain a variety of fluids some of which are toxic or flammable. For example, a large number of storage tanks are commonly used for storing gasoline below ground at service stations and above ground at refineries and storage depots.
Over time, metal storage tanks become corroded and perforate whereby the fluids or liquids which are stored therein leak or seep into the environment. Fibreglass tanks are susceptible to cracking, embrittlement, chemical attack and similar modes of failure, often sudden in nature, leading to leakage. This leakage creates environmental hazards as well as a potentially dangerous health risk to the public at large. Accordingly, a number of secondary containment devices have heretofore been developed to minimize the environmental hazards and dangers referred to above.
For example, U.S. Pat. No. 4,625,892 teaches a polyolefin lined tank consisting of a rigid pololefin tank within a metallic tank wherein there is no adherence or bonding between the walls of the inner polyolefin tank and the outer metallic tank.
Moreover, U.S. Pat. No. 4,651,893 illustrates a double-walled tank, or tank within a tank assembly comprising an inner tank, and outer tank, and spacer means for being positioned between and securely joined to the inner and outer tanks for defining a multi-channelled passage way between the inner and outer tank to allow for any leakage of fluid from the inner tank to pass there through.
U.S. Pat. No. 4,523,454 discloses a jacketing method consisting of a rigid inner tank encased by a flexible outer jacket with a leak detection means associated with the closed space between the tank and the jacket. This patent teaches the use of sheets of various materials such as rubber and the like. The resulting product is a jacketed single wall tank rather than a dual wall tank.
Another jacketing arrangement is disclosed in U.S. Pat. No. 4,685,327 which teaches a rigid inner tank with a manhead, a sleeve encompassing the manhead, a jacket encasing the inner tank and at least a part of the sleeve, and a dispensing line extending through the manhead into the storage tank's interior.
U.S. Pat. No. 4,607,522 is a continuation-in-part of U.S. Pat. No. 4,523,454 and illustrates a storage tank system for storing gasoline which comprises a rigid inner tank encased by a flexible outer jacket with a leak detecting means associated with the closed space between the inner tank and jacket and with a separate and distinct gas pervious material positioned between the tank and the jacket.
U.S. Pat. No. 4,653,312 teaches a method of making a jacketed storage tank which comprises applying a separating agent over the storage tank, applying a layer of fibrous reinforcing material on the separating agent, and thereafter applying a resinous material.
Finally, U.S. Pat. No. 4,640,439 discribes a double wall tank manufactured from a single wall tank by applying a spacing material to at least a portion of the exterior of the inner tank, stretching an imperforate film over the spacing material and finally applying a rigid outer sheath over top of the imperforate layer.
The storage tanks and methods of constructing same which have heretofore been employed present either relatively complicated structures or require methods of construction which are relatively time-consuming and expensive to complete or which require several distinct steps or separately applied layers.
It is an object of this invention to provide an improved method of making dual wall containers and in particular an improved method of constructing dual wall storage tanks for liquids.
It is a further object of this invention to provide an improved dual tank container and in particular, to provide a dual wall tank for storing liquids.
The broadest aspect of this invention relates to a method of making a dual wall container for storing fluids by: producing an inner wall for storing said fluid; positioning a fabric exteriorally against said inner wall; applying a liquid resin exteriorally to said fabric when said fabric is positioned exteriorally against said inner wall, so as to penetrate partially into said fabric such that, upon curing of said liquid resin, there is formed a outer wall for containing leakage of said fluid through said inner wall and an intermediate layer of fabric permeable to leakage of said fluid through said inner wall.
It is another aspect of this invention to provide a method of making a dual wall tank from a primary container adapted to store fluids, said primary container defining an inner wall, said method including the steps of: positioning fabric exteriorally against said inner wall; and then applying a liquid resin exteriorally to said fabric when said fabric is positioned exteriorally against said inner wall so as to penetrate partially into said fabric such that, upon curing of said liquid resin, there is formed an outer wall of cured resin for containing leakage of said fluid through said inner wall, a combined layer of fabric means penetrated with cured resin means, said combined layer integrally connected to said outer wall, and an intermediate layer of unpenetrated fabric disposed adjacent said inner wall, said intermediate layer permeable to leakage of said fluid from said inner wall.
It is another aspect of this invention to provide a method of manufacturing a dual wall storage tank for liquids comprising the steps of; producing a primary container for storing said liquid said container defining an inner wall; applying adhesive to the exterior surface of said inner wall; positioning permeable geotextile fabric against said exterior surface of said inner wall so as to adhere said fabric to said inner wall; and then applying chemically curing liquid resin exteriorally to said fabric when said fabric is applied to the exterior surface of said inner wall whereby said resin soaks partially into said fabric and, upon curing simultaneously forms an outer layer of cured resin; a combined layer of permeable geotextile fabric soaked with cured resin integrally joined to said outer layer so as to constitute together an outer wall capable of containing leakage of said fluid through said inner wall; an interstitial layer of unsoaked fabric disposed adjacent said inner wall, said interstitial layer permeable to leakage of said liquid through said inner wall of said primary container.
It is another aspect of this invention to provide a dual wall container for storing fluids comprising; an inner wall for storing said fluid; fabric disposed exteriorally against said inner wall, said fabric permeable to ,any leakage of said fluid through said inner wall; and substantially seamless outer wall of cured resin penetrating partially into said fabric for containing any leakage of said fluid from said inner wall.
It is yet another aspect of this invention to provide a dual wall tank for storing fluids comprising; a primary container for storing said fluid, said container defining an inner wall; an intermediate layer of fabric disposed exteriorally against said inner wall, said intermediate layer permeable to leakage of said fluid from said inner wall; a layer of said fabric combined with cured resin adjacent said intermediate layer; and a seamless outer wall of cured resin in the region of said fabric, said seamless outer wall integral with said combined layer for containing leakage of said fluid through said inner wall.
Finally it is an aspect of this invention to provide a dual wall tank for storing liquids comprising; a primary container for storing said liquid, said container defining an inner wall; an interstitial layer of permeable geotextile fabric disposed against the exterior surface of said inner wall; a layer of said geotextile fabric soaked with cured resin adjacent said interstitial layer; a seamless outer layer of cured resin integrally joined to said soaked layer and forming together therewith an outer wall for containing leakage of said liquid through said inner wall of said primary container.